A wide variety of sensors may be incorporated into portable devices, such as cell phones, laptops, tablets, gaming devices and other portable, electronic devices, as well as vehicles, such as drones, or other devices capable of relative motion. Notably, information from motion sensors such as gyroscopes, accelerometers, magnetometers that measure quantities along one or more orthogonal axes may be used to determine the orientation or change in relative orientation of a device incorporating the sensor for use as a user input, to determine positional or navigational information for the device, or for other suitable purposes. Sensors may also be provided for assessing other aspects of the environment surrounding the portable device, such as sound, humidity, pressure, light, the presence of chemicals and many others.
However, due to the nature of electronics and mechanics, including their relative size and materials and methods of construction, sensors may be relatively sensitive to ambient temperature and therefore may be subject to inaccuracies or errors depending on the ambient temperature or when the ambient temperature changes. A sensor may exhibit a temperature dependent offset or bias error that reflects a non-zero component of the output that is not correlated with the quantity being measured. The sensitivity of the sensor may also be affected by temperature, requiring different compensation coefficients. If these or other temperature dependent errors are not properly compensated, the quality of sensor data may be degraded. For example, many types of sensors may be implemented using microelectromechanical systems (MEMS) that may be constructed as a semiconductor package using complementary metal oxide semiconductor (CMOS) techniques on a silicon substrate or wafer having mechanically moving elements controlled by integrated electronics. As will be appreciated, ambient temperature may affect the performance of a MEMS sensor in a number of ways, the different materials used to construct the sensor may exhibit varying coefficients of thermal expansion, which causes changes in the manner that the elements respond to the environment and interact with each other. Voltage drift and other detrimental inconsistencies may also occur due to the ambient temperature or a change in ambient temperature.
One strategy for reducing the impact of ambient temperature on sensor performance is to determine performance characteristics of the sensor at a variety of operating temperatures. Subsequently, the operating temperature of the sensor may be determined and used to apply the appropriate correction to the sensor data being output. Correspondingly, any effect on the operating temperature caused by the ambient temperature may be compensated. As a practical matter, the relationships between temperature and sensor performance may be nonlinear and vary from device to device, requiring the inefficient and time consuming process of establishing the response of the output signal to temperature variations by operating the sensor at a known temperatures and measuring the resultant output signals. For example, the sensor device may need to be placed into an oven (or refrigerator) to hold the sensor at the given operating temperature while undergoing calibration and testing. At high volume productions, such individual calibration may be prohibitive due to lengthy heating time and complex test setup procedures.
To address these difficulties, a thermally stabilized sensor featuring an feedback controlled integrated heating or cooling element may be employed to maintain the sensor at a desired temperature. By providing a more constant operating temperature that is independent of the ambient temperature, the accuracy of a sensor may be improved. Nevertheless, significant drawbacks may be associated with thermally controlled systems. For example, energy is required to activate the thermal element to maintain the sensor at an the operating temperature different than would otherwise result from a given ambient temperature. Particularly for mobile applications, power resources may be limited and the need to heat or cool a sensor can reduce the effective operating time. The temperature regulating system may also require additional hardware complexity and cost. Accordingly, it would be desirable to provide systems and methods to improve thermal control of a sensor. For example, it would be desirable to reduce the amount of energy required to maintain a selected operating temperature. Likewise, it would be desirable to reduce the complexity of the thermal control system. Further, it would be desirable to increase the range of ambient temperature at which the sensor may operate reliably. As described in the following materials, this disclosure satisfies these and other goals. Although discussed in the context of MEMS sensors, the techniques of this disclosure may be applied to other technologies to improve the performance of any sensor whose output is affected by ambient temperature.